France will not negotiate with gunmen claiming to be from Nigerian Islamist group Boko Haram who have taken a French family of seven hostage, Defence Minister Jean-Yves Le Drian said on Tuesday.

The three adults and four children were seized in Cameroon's far north near the Nigerian border last week. In a video posted online on Monday, the gunmen threatened to kill them unless authorities in Nigeria and Cameroon released Muslim militants held there, reports Reuters.

"We do not negotiate on that kind of basis, with these kind of groups," Le Drian told RTL radio. "We will use all (other) possible means to ensure that these and other (French) hostages are freed."

"We do not play this bidding game because that's terrorism," he said, deploring the fact that children were involved.

The kidnapping has brought to 15 the number of French citizens being held in the region, with the risk heightened since Paris sent thousands of troops into Mali last month to help the country oust Islamists operating in the north.

Boko Haram has killed hundreds of people in an attempt to establish an Islamist state in Nigeria